题目(1)2x+5y−3x−9y(1)2x+5y-3x-9y(1)2x+5y−3x−9y；(2)2(3a2−ab)−(a2+2ab)(2)2(3a^{2}-ab)-(a^{2}+2ab)(2)2(3a2−ab)−(a2+2ab).知识点：整式化简求值章节：未标注
